Transcript EVD Emergency Vehicle Driver

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Physical Forces
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Physical Forces
 Directly Influence Control
 Offer Boundaries
 If Maintained – safe operation
 If Exceeded – loss of control
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Forces Acting on an Emergency
Vehicle







Velocity
Friction
Inertia
Momentum
Reaction
Centrifugal Force
Centripetal Force
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces




Inclement Weather
Excessive Acceleration
Inappropriate Braking
Sudden Direction change
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Velocity
 (Speed)
 “Rate of change of position in
relationship to time
 V = 35 feet every second (35 ft/sec)
 V = 55 miles every hour (55 MPH)
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Velocity Control
 Acceleration
 + Acceleration
 Deceleration
 - Acceleration
 (Coasting)
 Braking
 Deceleration using Friction
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Friction
 “Resistance to motion between to
moving objects that are in contact with
each other.”
 Generates HEAT
 Steering Friction
 Tire/Road Friction
 Brake Friction
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Friction
 Tire/Road
 Greatest – Stationary
 Ok – Motion on Dry, Smooth Road
 Least – Locked/Spinning
 Locked – Wheel NOT turning
 Spinning – Wheel FREE turning
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Friction
 Brakes
 Brakes on Drums / Pads on Discs
 Friction Generates Heat
 Heat Causes Brake Fade
 Will Break-down Bonding Material
 Heat/Expand Brake Fluid
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Brakes
 Shoes / Drums
 90%-10% / Contact-Cooling
 Excessive Heat = Less Contact
 Pad / Disc
 85%-15% / Cooling-Contact
 Excessive Heat = More Contact
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Brakes
 Locking Wheels
 Threshold Braking
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Inertia
 “The force it takes a moving object to
stay in motion in the same direction.”
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Newton’s First Law:
The Law of Inertia
“An object continues in its state of rest,
or uniform motion in a straight line,
unless it is acted upon by a
net external force.”
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Newton’s First Law:
The Law of Inertia
 Objects resist change
 More Mass = More Inertia
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Momentum
 Mass x Velocity
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Newton’s Second Law:
The Law of Momentum
“When an unbalanced force acts on an
object, the object will be accelerated. The
acceleration will vary directly with the
applied force and will be in the same
direction as the applied force. It will vary
inversely with the mass of the object.”
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Newton’s Second Law:
The Law of Momentum
 More momentum =
more energy to change
 1 lb @ 1 ft/sec = 1 unit of momentum
 Momentum & Intertia:
WORK AGAINST THE DRIVER
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
The Law of
Conservation of Momentum
“When two objects interact, exactly equal and
opposite forces result; positive and negative forces
balance out.”
“For a collision occurring between two objects, the
total momentum before the collision is equal to the
total momentum after the collision.”
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
The Law of
Conservation of Momentum
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Reaction
 “For every action there is an equal and
opposite ‘reaction.’”
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Newton’s Third Law:
The Law of Reaction
“For every action there is an equal and
opposite reaction.”
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Newton’s Third Law:
The Law of Reaction
 Tires push “backward” on the road
 Road pushes “forward” on vehicle
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Centrifugal Force
 An inertial force which moves a body
away from the center of rotation.
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Centripetal Force
 Forces directing the body towards the
center of rotation.
 Gravity
 Friction
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Centripetal Force vs.
Centrifugal Force
 Forces acting in direct contrast to
Centrifugal force.
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Directional Control
 Steering
 Turning
 “Tracking” curves
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Potential Energy
 Capability – i.e. Coiled Spring
 Relative to position
 “Stored” energy
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Kinetic Energy
 Relative to motion
 = ½mv2
 m = mass
 v = velocity
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Control
 ONLY
 VELOCITY
 & DIRECTION
Ref. Unit IV LP 1 (Lesson 8)
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Physical Forces
 Control
 Velocity
 Acceleration
 Change in Velocity
 + Acceleration = increase
 - Acceleration = decrease
 (Deceleration)
 Double Mass = Double Acceleration
 Generally thought of in the +
Ref. Unit IV LP 1 (Lesson 8)
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